The present invention relates to oil supplying structures for rolling element rows symmetrically arranged on both left and right sides of a guide rail of a linear guide apparatus. More specifically, the present invention is directed to an oil supplying structure for a linear guide apparatus which can be so mounted as to correspond to the angle of inclination of the linear guide apparatus, and which is, therefore, suitable for supplying lubricating oil equally to the rolling element rows on both sides irrespective of the magnitude of the angle of inclination.
As shown in FIG. 8, a linear guide apparatus generally includes: an elongated guide rail 1 having axially extending ball rolling grooves 3 symmetrically arranged on both side surfaces of the rail; and a slider 2 that mounts over the guide rail 1 so as to be movable relative to the guide rail in the axial direction and that has on inner side surfaces thereof ball rolling grooves 5 corresponding to the ball rolling grooves 3. A plurality of balls 6 are inserted into loaded ball rolling paths each of which is formed by both of the ball rolling groove 3 of the guide rail and the ball rolling groove 5 of the slider. These ball rows 6A circulate in endless circulating paths while rolling, each endless circulating path being formed by the loaded ball rolling path, a ball returning path 7 and curved paths 8. The slider 2 guided by the guide rail 1 is designed to move relative to the guide rail 1 in the axial direction through the rolling of the ball rows.
The ball rows 6A that repeat endless circulation during the operation of the linear guide apparatus are supplied with grease or oil. Generally, oil supplying is applied to a lubrication system by central oil supplying operation in automated lines and the like to which the grease is hard to supply. However, since oil is less viscous than grease and has fluidity, it is likely that insufficient oil lubrication results depending on positions where the oil is supplied in the operating aspect such as the linear guide apparatus is assembled with inclination.
For example, FIGS. 9 and 10 show an exemplary oil supplying structure for a conventional linear guide apparatus (conventional example 1). In the case of conventional example 1, an end cap 2B that is fitted to an end surface 2Aa of the main body 2A of the slider 2 mounting over the guide rail 1 has a square C-shaped branched oil passage 12 symmetrically arranged on a mounting end surface 2Ba thereof, the oil passage 12 communicating with an oil discharging hole 11 from a supplying port (not shown) on a side surface of the slider main body 2A. The oil flowing out into the branched oil passage 12 enters into a passage along the central portion of the axis of a semicylindrical return guide 13 that is fitted to the end surface 2Ba of the end cap 2B, then flows out into ball circulating curved paths 8 from supplying holes 14 in the wall surface of the return guide 13, so that the oil is supplied to the rolling balls 6. In this example as shown FIGS. 9 and 10, if the angle of inclination of the linear guide apparatus is 45.degree. with respect to the horizontal plane, then the angles of inclination .theta..sub.1, .theta..sub.2 with respect to the vertical line at which the branched oil passage 12 is branched out of the oil discharging hole 11 become equally 45.degree. (.theta..sub.1 =.theta..sub.2 =45.degree.). Therefore, the oil flowing out of the oil discharging path 11 reaches the pair of curved paths 8 on each of the left and right sides while being uniformly distributed at a corner portion 12a of the square C-shaped branched oil passage 12.
However, as shown in FIG. 11, when the angle of inclination .theta. becomes 60.degree., then the respective angles of inclination .theta..sub.1, .theta..sub.2 of the branched oil passage 12 become different from each other with .theta..sub.1 =30.degree. and .theta..sub.2 =60.degree.. As a result, a larger amount of lubricating oil flows into the branched oil passage 12 on the .theta..sub.1 side whose inclination is steeper. On the other hand, few lubricating oil flows into the branched oil passage 12 on the .theta..sub.2 side.
To overcome this problem, oil supplying structures are proposed in, e.g., Unexamined Japanese Utility Model Publication Nos. Hei. 2-21327 and Hei. 2-25719 (hereinafter referred to as "conventional example 2" and "conventional example 3", respectively).
As shown in FIG. 12, conventional example 2 is of a type which a linear guide apparatus is so mounted that two pairs of the ball rows 6A on both left and right sides of the guide rail 1 are inclined with one pair of ball rows being higher and the other pair of ball rows being lower. The conventional example 2 is characterized in that a branched oil path 16 having such an angle of inclination .theta..sub.1 =.theta..sub.2 as to allow the oil to be equally distributed corresponding to the mounting angle of inclination .alpha. is arranged within the slider main body 2A, so that the lubricating oil can be distributed to both pairs of ball returning paths 7 within the slider main body 2A from the supplying port 17 at the same angle.
Further, as shown in FIG. 13, conventional example 3 is also of a type which a linear guide apparatus is so mounted as to be similarly inclined, and characterized in that not only a supplying port 18 is arranged perpendicularly on the upper outer side surface of the main body 2A of the slider 2 to supply a pair of upper ball rows 19, but also the ball rolling grooves 3 symmetrically arranged on the guide rail 1 are communicated with each other through connecting oil paths 20.
The conventional example 2 is designed to uniformly distribute the oil to both pairs of ball returning paths 7 symmetrically arranged on the left and right sides within the slider main body 2A by arranging the uniformly branched oil path 16 previously corresponding to the mounting angle of inclination .alpha. of the linear guide apparatus. However, in fact, it is extremely laborious and time-consuming to machine the branched oil path 16 within the slider main body 2A so that the oil path 16 is branched at the angles of inclination .theta..sub.1 =.theta..sub.2 corresponding to the angle of inclination .alpha. of the linear guide apparatus.
On the other hand, the conventional example 3 is designed to cause the oil supplied to the pair of upper ball rows 19 of the obliquely mounted linear guide apparatus to flow into the pair of lower ball rows 19 through the connecting oil paths 20. However, in fact, if the angle of inclination .alpha. of the linear guide apparatus exceeds 45.degree., then most of the oil flows towards the pair of lower ball rows 19 via a clearance 21 between the upper surface 1a of the side rail 1 and the inner surface 2c of the slider 2 confronting the upper surface 1a. There causes a problem which the oil can hardly flow into the pair of upper ball rows 19.
Further, if the angle of inclination .alpha. is equal to or less than 45.degree., then the oil flows through the pair of upper ball rows 19 and then to the pair of lower balls rows 19 through the connecting oil paths 20. However, to arrange a plurality of connecting oil paths 20 along the elongated guide rail 1 raises the cost of manufacture. If, on the other hand, only one connecting oil path 20 is arranged, it is difficult to select a proper supplying timing.